1. Field of the Invention
The invention relates to an overcoat film composition, and more particularly relates to an overcoat film composition used, for example, for flattening a color filter for a liquid crystal display element, to a color filter substrate that is formed using the composition, and to a liquid crystal display element having the color filter.
2. Related Art
Acrylic compositions, polyimide compositions, and so forth have been put to practical use as overcoat film compositions for flattening out color filters used with liquid crystal display elements. These compositions exhibit their function as an overcoat film when applied to a color filter and then dried and calcined (Japanese Laid-Open Patent Applications H09-291150, 2001-158816, and 2005-105264). Since these overcoat films are incapable of aligning liquid crystals, however, it is necessary to further coat the overcoat film with an aligning film composition, then dry and calcine this coating to form an aligning film, and then bring out its characteristics as an aligning film by subjecting it to a rubbing treatment.
Meanwhile, if an aligning film is formed by coating a color filter with an aligning film composition without first coating with an overcoat film composition, the unevenness of the color filter cannot be flattened out because the aligning film is usually a thin film only about 0.1 μm in thickness. It is impractical, however, to form an aligning film composition as a thick film of more than 1 μm in order to achieve a flattening function because there will be a sharp decrease in transmissivity.